The monument to the 3rd Indiana Cavalry Regiment is north of State Route 34 just west of Antietam Creek. It was dedicated in 1910. (39.464177° N, 77.728028° W; see location)
The 3rd Indiana Cavalry was commanded at the Battle of Antietam by Major George H. Champan.
From the monument:
Companies A.B.C. D. E. & F.
3rd Indiana Cavalry, 2d Brigade
Cavalry Division, Lieut. Col. Jacob Buchanan, Commanding. Supported Tidball's Battery
at this point from 12 M. until 5 p.m.
September 17, 1862.
The 3rd Indiana Cavalry is also honored by a monument at Gettysburg.
See more on the 3rd Indiana Cavalry Regiment during the Civil War